After hearing Rabbi Lebowitz Shlit"a's quoting of Rav Schachter's opinion that it's permitted to bath in lukewarm water, I was very surprised to see the Reishit Bikkurim article (yutorah.org) page 5 which writes as Rav Schachter's pesak that it's forbidden to shower on yom tov in lukewarm water but only in water that's not uncomfertably cold, which he specifies is less than lukewarm. It probably is only a matter of degrees, but it's nonetheless a source to be pointed out.

I think that this is a great and informative shiur but just had one comment.

Rabbi Lebowitz says that it's very clear from Biur Halacha 511 D"H Yadav and Aruch HaShulchan 511:5 that the definntion of Shaave LeKol Nefesh changes according to the time and place. After looking up these sources I was unimpressed. Not only does it not mention place but even regarding time there's no proof. The Mishna Brurah (and Aruch Hashulchan) was only using this concept that the custom of the time can change in order to add a stringency and certainly not to create a leniency. The Bear Moshe 8:159 (which was quoted by Rabbi Lebowitz) actually makes this point that the proof from the Aruch Hashulchan (which is quoted from the Magan Avraham) is not a proof at all.